Discussion 3 - Biology 365R Handout for Discussion Sessions...

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Biology 365R Handout for Discussion Sessions Week of Sept 12 Objectives : To understand the concept of threshold and how it relates to ionic movements. To understand the phenomena of anode break excitation, the undershoot of the action potential, and the refractory period. To understand how the action potential is conducted. To understand axon conduction velocity and how it is related to myelination and axon size. To understand some simple molecular biology of ion channels. Discussion questions: 1. Give definitions for the following: depolarization, hyperpolarization, threshold, activation gate, inactivation gate, refractory period, anode break excitation, voltage clamp, patch clamp, Hodkin and Huxley, Neher and Sakmann. 2. Explain what is meant by a positive feedback between membrane depolarization and Na conductance. Given that Na channels behave in this fashion, why is it that a cell has a threshold—shouldn’t the cell fire an action potential whenever you depolarize it? Why not? Your answer should show you understand the concept of “threshold”. Is threshold for a given cell constant? How could it be changed? 3. What is the definition of threshold for a nerve cell? Explain what competing effects occur upon depolarization of a nerve cell membrane. Is the threshold of a nerve cell likely to be
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This note was uploaded on 09/19/2011 for the course BIO 320 taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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Discussion 3 - Biology 365R Handout for Discussion Sessions...

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